Synthesis, X-ray Structure, Magnetic Resonance, and DFT Analysis of a Soluble Copper(II) Phthalocyanine Lacking C−H Bonds

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• 作者：Hans Moons ; Ł ; ukasz Ł ; apok ; Andrei Loas ; Sabine Van Doorslaer ; Sergiu M. Gorun
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：October 4, 2010
• 年：2010
• 卷：49
• 期：19
• 页码：8779-8789
• 全文大小：1041K
• 年卷期：v.49,no.19(October 4, 2010)
• ISSN：1520-510X

文摘

The synthesis, crystal structure, and electronic properties of perfluoro-isopropyl-substituted perfluorophthalocyanine bearing a copper atom in the central cavity (F₆₄PcCu) are reported. While most halogenated phthalocyanines do not exhibit long-term order sufficient to form large single crystals, this is not the case for F₆₄PcCu. Its crystal structure was determined by X-ray analysis and linked to the electronic properties determined by electron paramagnetic resonance (EPR). The findings are corroborated by density functional theory (DFT) computations, which agree well with the experiment. X-band continuous-wave EPR spectra of undiluted F₆₄PcCu powder, indicate the existence of isolated metal centers. The electron-withdrawing effect of the perfluoroalkyl (R_f) groups significantly enhances the complexes solubility in organic solvents like alcohols, including via their axial coordination. This coordination is confirmed by X-band ¹H HYSCORE experiments and is also seen in the solid state via the X-ray structure. Detailed X-band CW-EPR, X-band Davies and Mims ENDOR, and W-band electron spin-echo-detected EPR studies of F₆₄PcCu in ethanol allow the determination of the principal g values and the hyperfine couplings of the metal, nitrogen, and fluorine nuclei. Comparison of the g and metal hyperfine values of F₆₄PcCu and other PcCu complexes in different matrices reveals a dominant effect of the matrix on these EPR parameters, while variations in the ring substituents have only a secondary effect. The relatively strong axial coordination occurs despite the diminished covalency of the C−N bonds and potentially weakening Jahn−Teller effects. Surprisingly, natural abundance ¹³C HYSCORE signals could be observed for a frozen ethanol solution of F₆₄PcCu. The ¹³C nuclei contributing to the HYSCORE spectra could be identified as the pyrrole carbons by means of DFT. Finally, ¹⁹F ENDOR and easily observable paramagnetic NMR were found to relate well to the DFT computations, revealing negligible isotropic hyperfine (Fermi contact) contributions. The single-site isolation in solution and solid state and the relatively strong coordination of axial ligands, both attributed to the introduction of R_f groups, are features important for materials and catalyst design.